When you're choosing between two similar foods at the grocery store, does the one that expires sooner somehow seem fresher, more natural or even healthier?
A new study suggests many of us make that connection. Across a series of experiments, consumers tended to see foods with shorter shelf lives as more natural and healthier than versions that lasted longer. That preference sometimes stuck even when researchers explained that better packaging, not different ingredients or processing, was responsible for the longer shelf life.
The findings, published in the Journal of Consumer Psychology, don't tell us whether shorter-lasting foods are actually healthier. Instead, the researchers wanted to understand how something as simple as shelf life can shape the way we judge food and decide what to buy.
They tested the idea using familiar grocery items, including potato chips, pasta sauce, mayonnaise and granola bars.
In one experiment, participants compared potato chips with shelf lives of five months and nine months. The five-month chips were seen as more natural and healthier.
But the nine-month chips had an advantage of their own: They were seen as more environmentally friendly and less likely to contribute to food waste.
That set up an interesting choice. What happens when shoppers have to weigh their preference for natural foods against their desire to waste less?
Researchers tested that question with pasta sauce. When participants were encouraged to think about the importance of eating natural foods, nearly 70% chose a sauce with a one-year shelf life over one that lasted three years. When environmental concerns were emphasized instead, only 43% chose the shorter-lasting sauce.
And the effect wasn't simply about people assuming longer-lasting foods contained different ingredients.
In another experiment, participants were told that one jar of mayonnaise lasted longer because it had a better seal. When naturalness was important to them, they still tended to favor the mayonnaise with the shorter shelf life.
Researchers found a similar pattern when people compared granola bars with nearly identical ingredients and nutrition information.
So why does the expiration timeline carry so much weight?
Yann Cornil, an associate professor at the UBC Sauder School of Business and a study co-author, said shoppers have a lot of information competing for their attention.
“We provide all the necessary information to make a rational choice. We provide ingredient lists. We provide nutritional facts. But it's a lot to process,” Cornil said.
Rather than weighing every detail, people may use quicker clues such as packaging, marketing and shelf life. In this case, a shorter shelf life can become shorthand for "more natural." And because people often connect natural foods with healthy foods, that assumption can affect how healthy a product seems, too.
But shelf life doesn't tell the whole story.
Some types of food processing can help products last longer, but so can improvements in packaging and food preservation. A product that stays fresh longer isn't necessarily more heavily processed or less nutritious simply because of the date printed on the package.
“To some extent they are correct, because the more you extend the shelf life of a food, the more likely it went through this ultra-processing technique … but not necessarily,” Cornil said.
The findings also raise an interesting question about food waste. If shoppers choose products with shorter shelf lives because they seem more natural, those foods may have less time to be eaten before they spoil.
“By looking for natural foods, consumers tend to prefer foods with a shorter shelf life, even though foods with a longer shelf life could be just as good, and just as healthy and natural, as we show in the paper,” Cornil said. “So by trying to choose natural foods, they might run the risk of choosing foods they will eventually waste because they have too little time to consume them.”
The study didn't track what happened to food after people brought it home, so it can't tell us whether these choices actually lead to more food waste. What it does show is that shelf life can influence how people think about a food before it ever reaches their cart.
And that influence proved surprisingly difficult to shake. Even when people could see nutrition information or knew better packaging was responsible for a longer shelf life, the date still shaped their impressions.
“The fact that we still find this effect even when we provide nutrition information, and even when we make consumers understand that packaging is responsible for the longer shelf life and not processing, is really interesting,” Cornil said. “And we go pretty far in showing the strength of this misleading heuristic.”
The research was supported by the Social Sciences and Humanities Research Council of Canada and the National Natural Science Foundation of China.